With the advance of technology, monitoring and control of a lighting device have become an important issue. Conventional light control and management are merely associated with controlling on and off of a lighting device. Operational parameters, such as voltage, current, circuit quality and failure rate of circuits of each lighting device are not made available for monitoring in real time. In the past, a light control system is usually constructed in a wired manner, which costs significantly and is difficult in maintenance. Even if a light control signal is transmitted in a wireless manner, relay stations are required for long-distance transmission of the light control signal. In addition, since the radio spectrum resources are limited, it is difficult to monitor and control all street lights which are widely spread.
In order to overcome this issue, a technology of Power Line Communication (PLC) has been developed. Considering that almost each corner of a house or an office building is provided with an alternating current (AC) power socket, more complicated communication of a control signal, such as a signal to change a pattern or a color of light emitted by a lighting instrument, may be achieved without the need to construct a new transmission line.
A communication interface adopted in a current light control system is a Digital Addressable Lighting Interface (DALI) interface. However, the DALI interface requires additional installation of signal lines which incurs further cost and complexity in constructing the light control system. If a power line, instead of the signal lines, is used to transmit a digital control signal and electric power, a pulse period or a pulse width of the digital control signal may be influenced by noise in the power line so that the digital control signal may not be demodulated correctly.